This invention relates to the detection of radioactive materials. More specifically it relates to a method and apparatus for the detection of radioactive materials using electromagnetic radiation. Even more specifically, the present invention relates to a method and apparatus for the detection of radioactive material by detecting the reflection of electromagnetic radiation from ion tracks created by alpha, beta, and gamma radiation.
It is well known that emissions from radioactive materials, alpha and beta particles and gamma rays, are extremely dangerous to both plants and animals. Various means to detect the presence of radioactive materials have been developed. One of the most common and well-known radiation measuring apparatuses is the Geiger counter. The Geiger counter detects the ionization that occurs in the atmosphere due to the presence of alpha and beta particles and gamma rays. A Geiger counter typically comprises a tube enclosing a cylinder cathode surrounding a rod-like anode. The cathode and anode are connected through an end wall of the tube to a source of electrical voltage. The tube is filled with a gas, usually a mixture of an inert gas, such as argon or neon, and a halogen, such as chlorine or bromine, at a low pressure, e.g., a few centimeters of mercury. A high voltage, e.g. 550 volts, is set up between the cylinder and the anode. This voltage is just a little less than that needed to create an electrical discharge between the two electrodes.
When a charged particle of sufficient energy enters the tube, it knocks electrons out of the atoms of the gas. These electrons, being negatively charged, are attracted towards the anode, and the atoms from which the electrons originated (which become positively charged ions) are attracted by the cathode. The high voltage established between the anode and cathode creates a high voltage gradient that accelerates the liberated electrons sufficiently to knock further electrons out of atoms, which in turn are accelerated by the high voltage gradient to knock still further electrons out of other atoms, creating an xe2x80x9cavalanchexe2x80x9d of electrons. As the avalanche of electrons continues, the positive ions are also accelerated towards the cathode wall. These positive ions strike the cathode wall with sufficient energy to release still additional electrons. All of these electrons descend on the anode wire and are detected as a pulse of electric current. The occurrence of this pulse thus indicates that a charged particle has passed through the tube. The electrical pulses can then be amplified and counted, using appropriate electronic counting circuitry, and/or converted to audible sound, to provide a user of the Geiger counter a quantitative and/or qualitative measure of the number of charged particles encountered by the Geiger counter.
An underlying problem with Geiger counters, and other radiation detecting apparatuses, is that they must be within the vicinity of the radioactive material to detect it. This means that they need to be carried to the area to be evaluated, exposing human personnel to the radiation. Even if carried by a remotely operated vehicle, the vehicle may be exposed to radioactive material and need to be cleaned before human personnel can safely come in contact with it.
Clearly, then, there is a longfelt need for a radioactive material detection apparatus that can detect the presence of radioactive materials from a distance, to prevent potential exposure of the apparatus and the user to radioactive material.
The present invention broadly comprises a method and apparatus for the detection of radioactive material in an area. The apparatus comprises a transmitter operatively arranged to transmit electromagnetic radiation, a receiver operatively arranged to measure an intensity of the electromagnetic radiation, and processing means operatively arranged to determine the presence of radioactive material based on the intensity measurement.
A general object of the present invention is to provide a method and apparatus to remotely detect radioactive material.
Another object of the present invention is to provide a method and apparatus to detect ion tracks in the atmosphere.